A solar cell array comprises a plurality of individual cells and interconnector means for electrically connecting adjacent cells in a matrix. Typically, the individual solar cells are arranged in columns and rows and the interconnector means are positioned so as to connect the cells in the requisite series and/or parallel circuit arrangement. The circuit arrangement, of course, depends upon the desired output voltage and current at the module peak power point.
Generally, for terrestrial applications, a solar cell array is fabricated and sold as a module comprising the solar cell array mounted on an electrically nonconductive support member having terminals provided therein. The module also has a top cover over the solar cell array. This cover is a transparent protective coating which protects the solar cells against environmental hazards and also serves to maintain the cells in proper position. The module typically is fitted into a metal frame which provides mechanical strength for the array and protects the solar cell array against damage due to environmental loadings, such as from wind, snow, ice, rain, etc. The metal frame also serves as a means for mounting the module at the proper angle to receive insolation.
The individual solar cells used in forming a solar cell array for terrestrial applications are circular discs or wafers having diameters generally in the range of 2 to 4 inches and formed from a polycrystalline silicon ingot which is melted, and then reformed into a cylindrical ingot of single crystalline silicon. The discs or wafers are then cut from the cylindrical ingot. These circular cells are quite common in commercial use because they are relatively less expensive per unit area than cells having another geometry. When the circular cells are arrayed, however, the total active surface area of the array, i.e. of the solar cells, is less than the area required for mounting the array. Thus, not all the solar radiation which impinges on the module is utilized, since only some of the solar radiation impinges on active solar cell areas and some of the radiation impinges on inactive areas between the circular solar cells.
A number of techniques have been proposed for increasing the efficiency and effectiveness of solar cell modules by focusing incident solar radiation onto active cell areas. For example, mirrors and the like have been proposed to reflect solar radiation and concentrate the radiation in a given area. In this regard, see U.S. Pat. No. 3,990,914, wherein a tubular solar cell is described which is mounted in a parabolic mirror for concentration of solar radiation onto the solar cells. Also, mention should be made of U.S. Pat. No. 2,904,612 describing a reflector-type device in which the land areas between the circular solar cells consist essentially of inverted intersecting frustums of cones circumscribing the cells.
Another technique employed to enhance solar cell module output is the use of lenses. In U.S. Pat. No. 3,018,313, for example, a solar cell module is described which has an array of lenses covering the module so as to concentrate the light impinging on the cover of the solar cell array to converge downwardly toward the active solar cell area. In U.S. Pat No. 4,053,327, yet another light focusing arrangement is described wherein the cover of a solar cell module comprises a plurality of converging lenses arranged so as to direct the light incident on the module so that it does not fall on the grid lines of the front electrode of the solar cells in the array. Yet another optical system for focusing incident radiation onto the solar cells so as to increase electric output and increase the efficiency of operation of such modules is disclosed in U.S. Pat. No. 4,042,417.
In addition to reflecting solar insolation from inactive areas of solar cell modules to the active areas of solar cells, it has also been proposed to use reflective surfaces below very thin solar cells so that light which penetrates the active solar cell area without being absorbed can be reflected back again to the active layer. See, for example, U.S. Pat. No. 3,973,994.
In U.S. Pat. No. 4,116,718, there is disclosed a solar cell module having a light diffusive member covering part of the area of the module not covered by solar cells. The diffusive member scatters incident solar radiation, some of which scattered radiation is ultimately absorbed by a solar cell.
In U.S. Pat. No. 4,235,643, a solar cell module is disclosed in which faceted light reflective surfaces are provided in the land area surrounding a plurality of circular solar cells arrayed on a support and encapsulated in an optical medium. Light incident on the reflective surfaces is thereby directed upwardly through the encapsulant and then downwardly, by internal reflection, toward the active surface of a solar cell.
Notwithstanding the advantages made in the past in increasing the efficiency of solar cell modules, there still remains a very definite need for a solar cell module which will utilize all the light energy that is available as effectively and efficiently as possible and importantly without the necessity of complex, expensive and environmentally vulnerable optical systems.